The present invention relates to new inorganic microporous solids having a framework structure consisting of AX.sub.4 -tetrahedrons linked by their edges and to a process for the preparation of these solids.
Crystalline aluminosilicates of the zeolite type have long been known and well defined (J. V. Smith; Chem. Rev. 88 (1988) 149). More than 64 structural types with well over 1000 variations, both of natural and of synthetic origin, are known under the term of "Molecular sieves" (W. M. Meier, D. H. Olsen: "Atlas of Zeolite Structure Types"; Second Edition, Butterworth, London (1987)). The common structural element of these oxo compounds consists of three-dimensional AO.sub.4 tetrahedrons (A=Si, Al) linked at all the corners (oxygen atoms). Their characteristic feature is that they have pores of a specified, variable size which imparts ion exchange and reversible adsorption properties to these compounds without bringing about changes in the structure forming network. These micro-porous solids have found many different uses (F.Schwochow, L. Puppe; Angew. Chem. 87 (1975) 659).
They are used for the adsorption of gases (purification of gas mixtures) and liquids (molecular sieve) (B. E. Ullmann, E. Biekert "Ullmanns Encyclopadie der Technischen Chemie", Volume 17, 4th Edition, published by Verlag Chemie, Weinheim (1972) page 9). They also serve as catalysts for various reactions (hydrogenation/dehydrogenation, cracking of crude petroleum hydrocarbons, isomerisation of alkanes) and for the separation of mixtures (Chromatography, Ion exchangers) (W. Hoderich, M. Hesse, F. Naumann; Angew. Chem. 100 (1988) 232). New applications, some of which are still in the state of development, are based on their property of ionic conductors (solid electrolytes) and as carrier material for enzymes and microorganisms (Biotechnologie) (G. A. Ozin, A. Kuperman, A. Stein; Angew. Chem. 101 (1989) 373).
Common to all the compounds described is that oxygen forms the electronegative part of the structural framework. In numerous compounds which have been synthesized, silicon or aluminium has been partly or completely replaced by other electropositive elements (B, P, Fe, Cr, Sb, As, Ga, Ge, Ti, Zr, Hf) (J. V. Smith; Chem. Rev. 88 (1988) 149). This has enabled compounds with modified properties to be obtained (W. Hoderich, M. Hesse, F. Naumann; Angew. Chem. 100 (1988) 232).
The systems described do not always fulfil the desired requirements, in particular as regards their strength and chemical resistance.